The present invention relates to an exposure information indicating device and, more particularly, to a photographic device for indicating the exposure information.
Generally, the calculation of exposure information is carried out under a first numbering system which is a so-called additive system of photographic exposure (APEX system) while the exposure information is expressed in a second numbering system. Therefore, it is necessary to convert the calculated APEX value under the first numbering system into the second numbering system. For example, in the case of aperture size, a numbering 1, 2, 3, 4, 5, 6, 7 and so on under the first numbering system, i.e., the APEX system, corresponds to numbering 1.4, 2.0, 2.8, 4.0, 5.6, 8.0, 11 and so on under the second numbering system. This second numbering system is well known as f/stop numbers.
Accordingly, in the conventional device, for the purpose of obtaining the values in the second numbering system with only the familiar numbers as described above, the calculated APEX value is approximated to an integral number.
For example, according to one conventional photographic device for indicating the exposure information, a plurality of reference levels are set for defining a plurality of regions between the two neighboring levels. A calculated value under the APEX system is compared with the reference levels for detecting a region in which the calculated APEX value falls. Thereafter, a previously set value of exposure information corresponding to the detected region is displayed through a suitable display means. For example, the display means can be 7-segment display elements coupled with decoders for digitally displaying the exposure information value or can be a spot illumination for pointing out one exposure information value from among a plurality of values. According to the above described conventional photographic device, the detected exposure information is not so precise, since one exposure information value represents all the calculated APEX values which fall in one region. Furthermore, since it is necessary to employ means for establishing a plurality of reference levels and to employ a particular circuit for the display means, the manufacturing cost therefor is quite high.
According to another conventional photographic device as disclosed in Japanese Laid-Open Patent Publication No. 58529/1977 published on May 14, 1977, the calculated APEX value is approximated to 1/2 of an integral number, that is, the calculated value may be one of 0, 1/2, 2/2, 3/2, 4/2, 5/2, . . . , n/2 (n is an integer). With respect to the above numbering, the corresponding f/stop numbers will be somewhat like 1, 1.2, 1.4, 1.6, 2.0, 2.4, 2.8, 3.4, 4.0, 4.8, 5.6, 6.7, 8.0, and so on. However, when f/stop value 6.7 is displayed, it will not be simple for an operator to understand immediately whether the unfamiliar f/stop value 6.7 means an f/stop closer to 5.6 or to 8.0 or at the exact middle between f/stop values 5.6 and 8.0.
A similar photographic device is shown in U.S. Pat. No. 3,909,137 to Toru Kisanuki.